Flow stabilizer for oil wells



G. C. STANLEY FLOW STABILIZER FOR OIL WELLS Dec. 19, 1961 2 Sheets-Sheet1 Filed June ll, 1956 INVENTOR GEORGE C. STANLEY.

BY E TORNEY Dec. 19, 1961 G. c. STANLEY FLOW STABILIZER FOR OIL WELLS 2Sheets-Sheet 2 Filed June l1, 1956 Om, om O O AI UmZON Iv nl m mZON I:

SOILVH "HO-SV@ INVENTOR GEORGE C. STANLEY. WM

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ATTORNEY 3,013,583 Patented Dec. 19, 1961 3,013,583 FLOW STABILIZER FOROIL WELLS George C. Stanley, 48 West Ave., Great Barrington, Mass. FiledJune 11, 1956, Ser. No. 590,683 3 Claims. (Cl. 13S-43) This inventionrelates to a flow stabilizer for the reduction by absorption offluctuations in velocities of fluids in oil wells, of which thereduction of fluctuations in velocities at sand faces of a selected typeof oil wells and resulting fluctuations in production rate isconsidered, below, as an example.

It has been recognized for some time that control of rate of productionof oil wells, and particularly with reference to controlling the ratioof gas and oil production, is of vital importance in maintaining optimumproduction rate and maximum yield. Thus, a recent authoritative industryreport states: Control of production rate is essential to any effectivemethod for improving production etliciency and, therefore, productionrate is perhaps the most important single factor which must beregulated. (Progress Report by the Special Study Committee of TheAmerican Petroleum Institute, [Dallas, 1942], pp. 18- 19.) Suitable flowcontrol devices have been demonstrated to produce productionimprovements of the order of twenty percent. Because head pressures inoil sands are approximately steady over brief periods of time,production rates are controllable by control of back pressures at sandfaces. For example, in 55 wells in the Pecos County, Texas, oil eld,average gas-oil ratios were reduced approximately 25% by the use oftapered tubing, which reduced the adverse influence of fluctuating backpressures, created by uniform sizes of tubing. In my previous Patent2,251,244, issued July 29, 1941, for Pressure Regulator, there isdisclosed a pressure regulating device incorporating means forautomatically leveling out iluctuations in the back pressure at the sandface of a well, but this mechanism involves operational difliculties andliabilities to failure which are unavoidable in automatic pressureregulating devices and the equipment is diflicult to service due to itsplacement at a rather deep point within the well. In general, controlmethods heretofore available have affected essentially only the averageworking conditions, whereas the actual conditions at the sand facefluctuate in a very marked manner due to pressure variations with eachstroke of the pump, in pumping installations, or pressure variation withslippage of gas in natural flow or gas lift installations. Usually, apetroleurn deposit is a sandy structure containing petroleum withdissolved and undissolved gas, and defined by a clay or rock dome orother interface on the top and water on the bottom. Too rapid withdrawalof oil and gas may permit the entrance of water adjacent the well andahead of the major part of the otherwise recoverable oil supply. Inother cases, dissolved and other gas which should be available forforcing the oil into the well from the surrounding sand structure, maybe dissipated, or excessive production rate may produce pressuredepletion even where the gas-oil ratio is initially not excessive. Inmany cases, there is an optimum pressure at the sand face and an optimumrate of production, which should be steady for best results. When thisrate isrexceeded, depletion will occur, typically, first at the sandface and then progressively further and further into the sand structure,ultimately causing one of the above`mentioned difficulties.

It is an object of the present invention to provide an improved methodand means for controlling the pressure conditions at the sand face in anoil well.

It is also an object to the invention to provide such a method and meansby which substantially constant conditions at the sand face may bemaintained.

In the drawing:

FIGS. l-A and l-B are, respectively, upper and lower central axialsections of an oil well embodying the invention in a preferred form;

FIG. 2 is an enlarged fragmentary axial section showing a pressureabsorption chamber; and

FIG. 3 is a chart illustrating variation in production of gas-oil ratioand rates of production.

In the important class of wells which have substantial free gas at sandfaces, low production rates create a diffusion type of flow,characterized by high gas-oil ratios and relatively low oil recoveries,as illustrated in FIG. 3. High production rates, in percent ofpotential, create excessive production rates, i.e., produce fluid out ofoil zones at rates greater than fluid is replaced into the criticalzones closely adjacent to the sand faces. This continuous phenomenoncreates excessive rates of pressure depletion, initially at sand faces,with resulting turbulent types of flow (meaning thereby turbulency,gas-slippage and/or flow through gas-channel flow-paths), with up-streamspreading, excessive gas oil ratios and relatively low oil recoveries.The optimum flowing conditions are between the above described low andhigh production rates. It has not heretofore been recognized that theconditions applicable to over all average production rate of an oil wellapply also and even more forcibly to the instantaneous condition withinthe well and particularly at the sand facerand in the adjoiningstructure. Thus, if at any given time, the sand face back pressure istoolow, a turbulent type of flow conditionsV described above is created,resulting in the blowing and wastage of gas, while if the pressure istoo high, a diffusion flow condition may result, in either caseincreasing rate of pressure depletion and the gaseoil ratio above theoptimum values which will necessarily occur at some intermediate sandface back pressure. In point of fact, where the sand face pressurelluctuates, as it commonly does, the flow conditions adjacent the sandface may periodically be reversed, creating a condition, so far asenergy loss is concerned, which is worse than any condition of diffusionor of a mere turbulent type of flow.

Even where the fluctuation in pressure at the sand face is apparentlysmall, and of the order of 1% or theref abouts, as, for example, afluctuation of about 5 p.s.i. with a total average pressure of 500p.s.i., the effect on production may be quite large, since thefluctuation is large with relation to the pressure drop from sand poreto sand pore in the structure adjacent the sand face. The best availableestimates as to the extent to which the pressure lluctuation willtransmit back into the sand-oil structure at a typical fluctuationfrequency such as 5 seconds, is about Sti-%, leaving an untransmittedfluctuation of the order of 0.5 to 1.0 p.s.i. This compares with anaverage pressure drop from adjacent sand pore to sand face of perhaps0.1 p.s.i. and it is quite apparent that the disturbance of flowconditions will be substantial.

In a well operated according to the present invention, there isinterposed between the source of pressure fluctuation, whether a pump orgas-oil column, and the sand face, a pressure regulating or absorbingdevice consisting essentially of a large number of pores or intersticescommunicating with each other through restricted flow passages, wherebythe pressure fluctuation must transmit back through a large number ofgas-filled cells and intermittently oil filled restricted orifices,which are arranged in series. It is apparent that a structure of thischaracter will even out pressure fluctuation to any desired extent. Thepressure regulator of the invention most conveniently takes the form ofa chamber filled with balls, preferably spherical and uniform in size.The balls may be of glass, ceramic, metallic, or other suitablesubstances, depending on the particular conditions, and their precisesize will not ordinarily be too critical.

In the drawing, there is indicated a well embodying the invention asapplied to a pumping well, FIGS. l-A and l-B being, respectively, upperand lower sections of the well. The structure in general isconventional. The outer casing 10, inner tubing 11, sucker rod 12,working barrel 13 and gas anchor 14 are all conventional. In the absenceof pressure regulating means according to the invention, pressurefluctuation such as above discussed would exist in a well of thischaracter. However, in the lower part of the tubing 11, there ispositioned a somewhat enlarged chamber 20 containing upper and lowerperforated diaphragms or headers 21 and 22, between which is containedand, preferably, packed, a mass of balls through which the oil andhitherto unseparated gas must flow on the way to the pump.

The balls 25 may conveniently be an eighth inch to one inch in diameterand the chamber containing the same may be of any desired length,depending upon operating conditions, a chamber ten to twenty feet inlength being suitable in many cases. The pressure uctuation absorptionchamber is best shown in FIG. 2. The enlarged tube or chamber 20 may beadvantageously as large as is conveniently accommodated by the outercasing 10, being connected to the inner tubing 11 by suitable reducers23. The parts will be screwed together or fastened together in any otherconvenient manner, so as to exert the pressure through partitions 21, 22on the mass of balls 25. These balls are preferably of uniform diameter,except for the top and bottom layer 25' or two, which may beconsiderably larger for the purpose of preventing blocking of the vholes26 in the headers or diaphragms 21, 22. While the adjustment of distancebetween headers 21 may be made in various ways, the upper header 21 isconveniently carried by a threaded sleeve member 27 which is screwedinto the tubing 20, as indicated, and may be held in place by thethreaded locking member 23.

As will be understood, the parts are preferably dimensioned so as toposition the entire chamber between headers 21 and 22 as well as thepacker 29, below the solid uid level.

What is claimed is:

1. In an oil well installation, pressure fluctuation absorbing meanscomprising a tubing section forming part of the gas-oil tlow path,perforated headers at the top and bottom of said section, and a mass ofballs in the space between said headers and filling said space,confining and restricting the ow path therebetween to a large number ofrelatively small interstices connected by restricted ow passages.

2. In an oil well installation, pressure fluctuation absorbing meansaccording to claim l, comprising open tubing sections above and belowsaid headers and continuing the rst said tubing section.

3. In an oil well installation, pressure fluctuation absorbing meanscomprising a tubing section forming part of the gas-oil flow path,perforated headers at the top and bottom of said section, and a mass ofballs in the space between said headers, contining and restricting theflow path therebetween to a large number of relatively small intersticesconnected by restricted ow passages, the said mass of balls filling saidchamber and being pressed together between said headers.

References Cited in the le of this patent UNITED STATES PATENTS 644,171Handler Feb. 27, 1900 1,232,456 Bliss July 3, 1917 2,020,412 HandlerNov. 12, 1935 2,342,904 Sledge Feb. 29, 1944 2,462,929 Zodtner Mar. 1,1949 2,665,644 Wells Jan. 12, 1954 2,748,802 Hanson et al. June 5, 1956

